1. Field of Invention
The present invention relates to a method and an apparatus for forming a linear scribed groove on a workpiece.
2. Description of the Related Art
In general methods of forming a scribed groove or hole for division on a workpiece, the position irradiated by a laser beam on the workpiece is moved while irradiating the laser beam from a laser beam source to be focused on the workpiece. In laser scribing of ceramics and the like, a Q switch laser is generally used as a laser beam source.
Scribed grooves and holes are preferably as deep as possible since cutting of the workpiece can be executed more easily and correctly. However, for increasing the depth of the grooves and holes, it is necessary to elevate the power density or the energy density of the focused laser at a position on the laser workpiece. Thus, in the case in which the laser output power is limited, deeper scribed grooves can be realized by prolonging the irradiation time of the laser beam (i.e., declining the scanning rate of the laser beam); however, to prolong the irradiation time may result in deteriorated productivity. Therefore, it is necessary to increase the output of the laser beam for quick scribing of a scribed groove having a predetermined depth, but increase of the output is not preferred since a high cost is required for the laser.
In laser scribing, a variety of other improvement efforts have been made in order to enable a workpiece to be cut more easily and correctly.
In one exemplary method, a plurality of pulsed laser beams are irradiated on a workpiece while moving the irradiation positions of the plurality of pulsed laser beams. The irradiation positions of the plurality of pulsed laser beams are moved such that a pulsed laser beam is irradiated on holes which had been formed in advance by the plurality of pulsed laser beams (for example, see pamphlet of PCT International Publication No. WO2006/006850).
According to such a method, the apparatus must be complicated, which can be disadvantageous also in cost since controlling is necessary for irradiating a laser beam on a portion where the hole had been formed in advance.